1. Field of the Invention
The present invention relates to a lens-fitted photo film unit and a method of unloading a cassette from the same. More particularly, the present invention relates to a lens-fitted photo film unit containing a photo film cassette in which a photo film port shutter is disposed, and a method of unloading the cassette from the lens-fitted photo film unit.
2. Description Related to the Prior Art
A lens-fitted photo film unit is known, and sold under a trade name such as "Fujicolor Quick Snap Super 800" (manufactured by Fuji Photo Film Co., Ltd.). The lens-fitted photo film unit includes a housing, which incorporates a simple shutter mechanism, and is pre-loaded with unexposed photo film. When a user purchases the lens-fitted photo film unit, he or she can take an exposure readily with it. In the lens-fitted photo film unit, a winding wheel is engaged with a spool inside a cassette shell. After effecting one exposure in one frame, the winding wheel is rotated to wind the photo film into the cassette shell as much as one frame. After taking exposures in all frames on the photo film, the lens-fitted photo film unit is forwarded to a photo laboratory, where a bottom lid of a cassette containing chamber is opened to unload the cassette shell by moving it down axially.
There are various suggestions to include a new plastic type of photo film cassette in the lens-fitted photo film unit. The photo film cassette does not have plush or light-trapping fabric in a photo film passage port, but has a plastic photo film port shutter, which is rotatable between an open position and a closed position. In the open position, the passage port is open. In the closed position, the passage port is blocked. To open and close the port shutter, a drive shaft of a camera or lens-fitted photo film unit is fitted on the port shutter and is rotated in forward and backward directions. A lock claw or pawl is disposed inside the cassette shell and has rigidity and resiliency. When the port shutter has the closed position, the lock claw is engaged with an engaging portion at an axial end of the port shutter, and keeps the port shutter from being rotated by incidental shock.
A commonly assigned patent U.S. Pat. No. 5,452,036 (corresponding to JP-A 6-130558) also discloses the lens-fitted photo film unit in which the cassette shell is used. A lock member is disposed on a bottom lid of the cassette containing chamber, and engaged with the port shutter of the cassette shell. While the lock member locks the bottom lid, the port shutter has the open position. When the lock member is released from the locking, the port shutter is rotated to the closed position.
There is a problem in the disposition of the lock member on the bottom lid, as the lock member thickens the bottom lid to increase the height of the lens-fitted photo film unit, which should be compact in the size. Another problem lies in laboriousness in operation of releasing the lock member to open the bottom lid. Photofinishing operators must handle a great number of lens-fitted photo film units. The low operability of the lock member hinders efficiency in the photofinishing from being improved.
To solve these problems, it is conceivable that a rotating member is disposed on the top of the cassette containing chamber, is engaged with the port shutter, and causes the rotating member to the closed position in response to opening the bottom lid. However a problem is still likely to occur: the rotating member after rotating the port shutter to the closed position is squeezed or stopped by the lock claw. The cassette shell is likely to fail to exit from the cassette containing chamber even when the bottom lid is open. The cassette shell could be unloaded by shaking or shocking the housing. But there would be possibility of dropping the cassette shell and striking the cassette shell against a floor or a wall of a room. The cassette shell might be broken incidentally to subject the photo film to ambient light. Alternatively a tool such as a screwdriver could be used to scrape out the cassette shell. However the cassette shell would be scratched to have the appearance damaged. The use of the tool would be inefficient.
The lock claw locks the port shutter when the rotating member is moved away from the engaging portion after rotating the port shutter to the closed position. However the lock claw cannot be engaged with the engaging portion if the port shutter is shifted rotationally in an accidental manner at the time of disengagement of the port shutter from the rotating member. There is no known technique capable of keeping orientation of the cassette shell in the rotational direction before the disengagement of the port shutter from the rotating member.